The present invention relates to an optical disk recording system which forms a visible image on a disk surface of an optical disk, such as a CR-R/RW, a DVD+R/RW, or a DVD-R/RW, by use of a laser.
Recording a visible image, such as characters or graphics, on a recording surface of an optical disk or a label surface (a surface opposite the recording surface) of the same by use of a laser has been known.
For instance, Patent Document 1 proposes a technique of providing a visible light characteristic changing layer at a position which is viewable from a label surface side of an optical disk; and exposing the visible light characteristic changing layer to a laser beam to thus change a visible light characteristic of the layer and render a visible image.
Patent Document 2 proposes a technique of using a reversible phase change material for a recording film of an optical disk, which enables recording of a visible image by use of a laser, and rewriting recorded graphics.
Patent Document 3 proposes a technique of newly writing a visible image on a recording surface of an optical disk on which a visible image has already been recorded.
Patent Document 4 proposes a visible image recorder capable of preventing occurrence of a failure of adjacent pixels in a visible image to be recorded at separated positions to thus record a visible image, differing from the original image, which would otherwise be caused when the visible image has been brought out of focus by a servo during recording of a visible image.
Patent Document 4 also describes, as a way to determine an angle position θ, a technique of determining a single rotation from a predetermined number of cycles; generating a pulse signal every predetermined number of cycles; and determining an angle position by means of the number of pulses (FIG. 6).
Patent Document 1: JP-A-2002-203321
Patent Document 2: JP-A-2003-016649
Patent Document 3: JP-A-2004-039019
Patent Document 4: JP-A-2004-030832
The invention described in Patent Document 4 describes out-of-focus but provides no description about “buffer under run.”
“Buffer under run” is an interruption of recording which can arise irrespective of focus control. An interruption of recording attributable to out-of-focus and an interruption of recording attributable to “buffer under run” are totally different from each other in terms of the amount of data which remain in a buffer of an optical disk drive unit at the time of occurrence of the interruption. As above, “buffer under run” is a phenomenon which cannot be predicted from out-of-focus, and hence out-of-focus and “buffer under run” cannot be discussed in the same terms.